. >> we've created a better environment for these organisms. the organism enters the lungs. usually the patients present with symptoms of weakness, a persistent cough. they can have night sweats. their oxygen exchange in the lungs is not so good, so they're always weak. >> we've had 400 different patients with microbacteria. >> reporter: pulmonologist dr. david says most people are not acceptable to the bacteria, but for those who have a history of lung problems, for elderly patients and people with compromised immune systems, ntm can be life-threatening. >> you can see the crud that i picked up. >> reporter: and the proof is right in front of us as he takes off a showerhead. >> this has got lots of it. >> reporter: for katie, life has changed dramatically. no more showers and she only drinks bottled water. but at least she's finally feeling better. >> there's so many different ,,, >>> weather time. meteorologist pa deanno with the forecast. boy, do we see a big change, especially in downtown san francisco. we literally changed seasons in like two hours. look at the differen